ELECTRONICS

There are only two pressure vessels on the Stingray that house its main electronics: the computer box and the battery box.

The Computer Box

The computer box consists of a resealable
aluminum housing designed by the iBotics team. The internal cavity of
this enclosure was designed to be the exact dimensions to fit the main
computer, an inertial measurement unit (IMU), a video frame grabber, a
data acquisition card, and a moisture sensor in their most
space-efficient configuration.

The main computer of the Stingray is a Kontron ETX-CD Intel Core 2
Duo based single board computer. The board has a dual core processor
running at 1.2GHz, 2GB of DDR2 RAM, 100Mbps Ethernet port, and VGA
support. Ubuntu Linux is used as the operating system.

The Labjack U3-HV5 A/D data acquisition card is used to monitor
and collect data from a number of the onboard sensors. The data
acquisition card communicates this information to the main computer
through USB.

As the computer box contains the Stingray's most expensive and
essential electrical components, the iBotics team designed and built a
custom moisture sensor that indicates if the amount of moisture in the
computer box ever reaches a potentially dangerous level. The moisture
sensor spans the base of the computer box underneath the main computer
and is monitored by the data acquisition card. To further protect
against potential component failure due to moisture, a few desiccant
packets are also sealed in with the electronics.

The Battery Box

The second pressure vessel is used to house the
power components: two lithium polymer batteries, five electronic speed
controllers, power regulators, the e-stop relay circuit and fuses. The
battery box is constructed from a modified Pelican case.

A 4 Amp-hour 14.8V lithium polymer battery is used to power the
main computer and its peripherals including the data acquisition card
and sensor array. A second 8 Amp-hour 11.1V lithium polymer battery is
used to power the propulsion systems. A Scorpion Commander 45Amp
electronic speed controller is used to manage power to each of the
motors on the Voith-Schneider propellers. Each of the vertical thrusters
is driven by a Castle Sidewinder 25Amp electronic speed controller.

Each of the batteries is connected in series to a 30Amp slow-blow
fuse as a redundant hardware safety measure in case the current drawn
from any of the electrical components becomes abnormally large,
signaling an electrical short or some other potentially dangerous
condition, and software is unable to detect and correct the situation.